Three-dimensional (3-D) printing, which works by building parts in layers, is a process used for the building up of three-dimensional models. 3-D printing is relatively speedy and flexible allowing for the production of prototype parts and tooling directly from a CAD model, for example.
Using 3-D printing enables the manufacturer to obtain a full 3-D model of any proposed product before tooling thereby possibly substantially reducing the cost of tooling and leading to a better synchronization between design and manufacturing. A lower product cost and improved product quality can also be obtained.
Various systems have been developed for computerized three-dimensional printing. Known systems include a system developed by 3D Systems Inc. of California, USA, which operates on the basis of stereo-lithography wherein a focused ultra-violet laser is scanned over the top of a bath of photopolymerizable liquid polymer plastic material. The surface of the bath is polymerized on contact with the UV laser creating a solid plastic layer at or just below the surface.
U.S. Pat. No. 5,387,380 to Cima et al. describes a technique for providing layered parts by depositing a layer of powder material and then depositing a binder material in selected regions to produce a layer of bonded powder material at the selected regions. These steps are repeated for successive layers to form a desired component. Following heat treatment, unbound powder is removed, leaving the fabricated part.
U.S. Par. No. 5,287,435 to Cohen et al describes apparatus for producing three-dimensional models which includes apparatus for depositing layer-by-layer, a photopolymer material in a selectable configuration and apparatus for curing each layer prior to deposition of the succeeding layer.
A disadvantage of this system is that it is difficult to achieve a flat uniform surface for each layer. U.S. Pat. No. 5,287,435 utilizes a machining unit for trimming the surface of each layer to remove excessive thickness.
In standard two-dimensional printing, the ink jet printer prints parallel ink dot lines on a substrate by displacing its print head relative to a substrate in one direction during the actuation of its ink jet heads.
In order to print an image of a desired line resolution, each ink jet head is required to print a number of ink dot lines equal to the ratio between the separation gap between ink jet heads and the desired line resolution. In practice, this is achieved by intermittently advancing the print head relative to a substrate in a second direction perpendicular to the first direction through one or more steps and actuating the ink jet nozzles at each of their new positions whilst displacing the print head relative to a substrate in the first direction. Unfortunately, if one or more nozzles are blocked, the image will be imperfect, having unprinted bands.
Patent WO 97/31781 assigned to Idanit Technologies Ltd of Israel describes a method for operating an ink-jet printer, having a linear row of nozzles, which displaces the print head relative to the substrate in a direction which is transverse to the line being printed and repeating the printing steps. This method reduces the visual effect of an unprinted band due to a blocked nozzle by the displacement of the print head but does not compensate for the blocked nozzle completely.